In the case of dysphagia, swallowing becomes difficult in eating and drinking, and a patient is often forced to give up eating and drinking through the mouth, nutrition intake, which raises a great problem from the viewpoint of QOL. At the same time, mental and physical stress on a caregiver who cares for eating and drinking becomes very heavy. Further, the percentage of pneumonia in causes of death in the elderly increases sharply, and a most part thereof is believed to be aspiration pneumonia caused by dysphagia.
Onset of dysphagia is frequently caused by disorder of basal ganglia derived from cerebral vascular disorder, Parkinson's disease, aging, excessive administration of an antipsychotic drug, or the like. By reduced activity of the nigrostriatal dopaminergic neurons in the site, synthesis of substance P, which is up-regulated by dopaminergic neurons, is decreased. When the synthesized substance P is released from a nerve terminal of the vagal nerve and the glossopharyngeal nerve sensory branch, a swallowing reflex is elicited. Therefore, decrease in the amount of substance P decreases a swallowing reflex to trigger aspiration, and especially when intraoral bacteria enter into the lung by inapparent aspiration, they can cause aspiration pneumonia. Consequently, improvement of a swallowing reflex in eating and drinking is quite important for a person inconvenienced by dysphagia to improve their QOL, and for caregiver to reduce the burden, as well as to prevent aspiration pneumonia.
Conventionally, as a treatment method for dysphagia, rehabilitation has been practiced. However, the rehabilitation requires sometimes unreasonable endeavor of a relevant person, and is applicable not to all symptoms. As a treatment using a drug or the like, the following Non-Patent Literature and Patent Literature report as a conventional example that capsaicin, a pungent component, promotes release of substance P from a nerve terminal and improves swallowing reflex (Patent Literature 1), but also report that continuously use of capsaicin induces depletion of substance P. Further, it is suggested that a preparation used for a treatment of Parkinson's disease, such as levodopa and amantadine, improves dysphagia by acting on dopaminergic neurons in the nigrostriatum (Non-Patent Literature 1), but due to side effects administration must be done cautiously. Meanwhile, an angiotensin converting enzyme participates in degradation of angiotensin I as well as substance P as substrates, and therefore it is inferred that by administration of an angiotensin converting enzyme inhibitor degradation of substance P is suppressed and dysphagia can be improved, and further it is reported that onset of pneumonia can be suppressed (Non-Patent Literature 1). However, in order to inhibit the action of an angiotensin converting enzyme by oral administration, an angiotensin converting enzyme inhibitor is used in the same dosage as that used as an antihypertensive agent, and therefore care needs to be taken in using the inhibitor, because the inhibitor decreases the blood pressure of a person with a normal blood pressure or even with a low blood pressure. Especially in the case of an aged person, excessive reduction of the blood pressure may have various negative influences, such as dizziness, lightheadedness, sleeplessness, and fatigue, as well as decrease in an intracerebral blood flow amount.